Balanced fork lift truck

ABSTRACT

A balanced fork lift truck comprising a motorized steerable chassis having upright elevator masts tiltably mounted on opposite ends thereof, means for effecting inward tilting of the respective masts, and outwardly projecting load lifters supported on the respective masts for raising and lowering movements therealong, whereby loads can be picked up at both the forward and rearward ends of the vehicle and carried simultaneously to new locations where the loads can be individually redeposited by the truck.

United States Patent [191.

Spratt 1 June 4, 1974 BALANCED FORK LIFT TRUCK [76] Inventor: Richard J. Spratt, 8623 So.

lngleside, Chicago, 111. 60619 [22] Filed: June 14, 1971 [21] Appl. No.: 152,540

[52] US. Cl. 214/660, 187/9 [51] Int. Cl B661 9/16 [58l Field of Search 214/660, 672, 673, 674, 214/620, 750; 187/9 [56] References Cited UNITED STATES PATENTS 2,480,066 8/1949 Weaver 182/16 2,910,203 10/1959 Todd 214/75 R 3,032,220 5/1962 Love 214/620 3,045,853 7/1962 Card, Sr 214/672 3,092,268 6/1963 Powers 214/670 3,257,013 6/1966 Arnold 180/77 S 3,526,329 9/1970 Anderson ct al. 214/140 Emke .1 214/750 Peterson et a1 214/140 Primary Examiner-Gerald M. Forlenza Assistant Examiner-Lawrence J. Oresky Attorney, Agent, or Firm-Burmeister, Palmatier & Hamby [57] ABSTRACT 1 Claim, 6 Drawing Figures PATENTEUJun'Mm SHEEI 1 BF 2 PAT ENTEDJun 4 I974 SHEET 2 BF 2 1 BALANCED'FQRK ur r TRUCK This invention relates to motorized fork lift trucks which pick up, carry and carefully deposit in new locations materials that are normally held together intrinsically or by bundling, packaging or containerization in such fashion that handling by a fork lift truck is feasible. Bundles of lumber held together by steel strapping are good examples of heavy objects handled to advantage by fork lift trucks.

Basically, a conventional fork lift truck comprises an elevator carried on the front end of a motorized wheeled vehicle. The object to be carried is lifted by a pair of generally horizontal tines or forks which project forwardly from a carriage or frame which is elevated along a mast that is tipped somewhat inwardly after loading of the forks.

As used for picking up heavy objects and bundles and redepositing such in new locations, fork lift trucks afford unparalleled advantages. However, as hauling vehicles, conventional fork lift trucks are highly inefficient and, as a consequence, are used for transporting materials normally over rather short distances.

The load carrying capacity of a conventional fork lift truck of given size and weight is severely curbed by the fact that the entire load and the elevator structure which supports the load are carried far forward of the center of gravity of the vehicle. The load thus tends to unbalance the vehicle making it unstable.

Rearwardly mounted ounterweights, which compensate somewhat for the unstability inherent in fork lift trucks, add heavily to the deadweight of the vehicles creating further inefficiencies.

Because of its inherent instability and the consequent necessity to limit loads to avoid capsizing, the conventional fork lift truck has a load carrying capacity limited to a weight value far below the inherent load supporting capability of the vehicle itself. Typically, conventional fork lift trucks of a given deadweight have a load carrying capacity that is severely restricted in relation to the capacity of other self-propelled trucking vehicles.

One object of the present invention is to provide a new and improved motorized fork lift truck which has, for a vehicle of given size and weight, an overall load bearing capability that is .decidedly and most advantageously increased in relation to that of conventional fork lift trucks.

A further object is to provide a new and improved fork lift truck which affords all the inherent advantages of conventional fork lift trucks while at the same time providing an increased load bearing capability and an inherent stability and balance lacking in conventional fork lift trucks.

Another object is to provide a new and improved fork lift truck having balanced load bearing capabilities that materially increase, in relation to the size and weight of the vehicle, the load supporting capability of the truck and the distances over which objects can be economically moved by such trucks.

A further object is to provide an improved, long range fork lift truck of balanced load bearing capabilities of the character recited in the preceding objects which is inherently well adapted for economical manufacture using proven manufacturing technology and components.

Other objects and advantages will become apparent from the following description of the exemplary embodiment of the invention illustrated in the accompanying drawings, in which:

FIG. 1 is a side elevational view of a balanced fork lift truck incorporating the invention, wherein certain major internal components and alternative working positions of major external components are illustrated in phantom;

FIG. 2 is a plan view of the improved fork lift truck of FIG. 1;

FIG. 3 is a vertical sectional view, somewhat simplified, taken with reference to the line 3-3 of FIG. 1;

FIG. 4 is a generally horizontal sectional view taken with reference to the line 4--4 of FIG. 1;

FIG. 5 is a simplified rear end view taken with reference to the line 5-5 in FIG. 4; and

FIG. 6 is a fragmentary vertical sectional view taken with reference to the line 66 in FIG. 4.

Referring now to the drawings in greater detail, the new and improved fork lift truck 10, FIG. 1, incorporating the invention comprises a motorized chassis 12 having forward support wheels 14 and rearward support wheels 16, the latter being steerable by means of a steering wheel 18 conveniently positioned forwardly of an operators seat 20. l

A driving motor 22, which may be an internal combustion engine, is mounted on the chassis l2 and connected through a suitable transmission 24, as indicated schematically in phantom in FIG. 1, with the forward support or traction wheels 14 to drive the latter and propel the vehicle either in forward or reverse directions selectively, the movements of the vehicle being controlled by the transmission 24 and the steerable rear wheels 16.

A forward tiltable elevator mast 26 is supported in a generally upright position on the forward end of the chassis 12 for tilting movement about a pivotal axis 28 extending transversely in relation to the vehicle at the lower end of the mast 26 as depicted by a dot in FIG.

Controlled tilting of the forward mast 26 is effected hydraulically in the instant machine by means of a pair of hydraulic cylinders 30 anchored to the chassis l2 and connected to the mast 26 in spaced relation to the pivot axis 28.

A forward load lifter 32 is supported for translation along the generally vertical mast 26 to be controllably raised and lowered along the mast 26 by hydraulically energized power elevating means 34, which may be of a generally conventional construction as such, carried within the mast 26 and connected to the load lifter 32.

As shown, the forward load lifter 32 comprises a pair of load supporting tines or forks 35 projecting forwardly from the lower edge of the load lifter structure translatable along the mast.

Raising and lowering of the forward load lifter 32 and rearward tilting of the mast 26 are effected under power in this instance by manipulation of hydraulic control levers 38 positioned as shown in FIG. 2 alongside the operators seat 20.

With the forward load lifter 32 in a lowered position, the vehicle 10 is maneuvered by the steering wheel 18 and transmission 24 to slip inforward forks 36 under the object (not shown) to be lifted, whereupon the load lifter 32 is raised along the mast 26 suspending the load on the forks 36 and the mast 26 is tipped somewhat 3 rearwardly so the load is held by gravity against movement off the outer ends of the forks.

A rear tiltable elevator mast 40 is pivotally mounted on the rear end of the vehicle chassis 12 in a generally upright position for swing movement about a pivotal axis 42 extending transversely in relation to the vehicle near the lower end of the mast 40. The rear mast 40 is controllably tilted somewhat about the axis 42 by a pair of hydraulic cylinders 44, FIGS. 1 and 4, anchored to the rear end of the vehicle chassis l2 and connected to the mast 40 about the axis 42 as shown.

A rear load lifter, denoted generally by the number 46, is supported on the rear mast 40 for translation therealong to be raised and lowered by rear power elevating means 48 incorporated within the rear mast 40 and connected with the rear load lifter.

Preferably, the rear mast 40 comprises a vertically extendible inner section 50 supported by a lower mast section 52, F lG. 4,-into which the extendible section 50 is retractable as shown in FIG. 1. In the preferred construction illustrated, the upper end of the lower mast section 52 andhence the upper end of the rear mast50, when collapsed, is generally on a level with the operators seat 20.

The rear load lifter 46 comprises, as shown best in FIGS. and 6, a generally vertical carriage frame 54. Preferably, thecarriage frame 54 comprises three substantially coplanar support plates 56 spaced somewhat apart, as shown in FIG. 5, and extending horizontally on edge between two generally vertical side plates 58 to which the ends of the plates46 are fixedly secured as by welding.

A pair of vertically extending roller support plates 60, FIGS. 4 and 6, are welded to the backsides of the horizontal support plates 56 to extend vertically along the backside of the carriage 54 in perpendicular relation to the support plates 56. The two vertical roller support plates 60 carry at their upper and lower ends support rollers 62 which fit into the extendible section 50 of the mast 40 to support the carriage 54 on the rear mast 40 to be raised and lowered by the rear elevating means 48 which is connected to support the carriage-54 by chains 64, FIG. 4, anchored to suitable anchors 66 fixed to the backside of the carriage support plates 56, FIG. 4.

A rear' fork support bar 68, FIGS. 4 to 6, forming part of the carriage 54 extends horizontally between the upper ends of the carriage side plates 58 which support opposite ends of the bar 68. Two rear load lifting forks 70, each having a generally L-shape as viewed in profile, FIG. 1, are pivotally supported on the upper carriage bar 68 to swing from an out-of-the-way inactive or stowed position, shown in solid lines in FIGS. 1 and 2, to active load bearing positions illustrated in phantom in FIGS. 1 and 2.

The two rear load lifting forks 70 are dimensioned and spaced horizontally from each other along the rear fork support bar 68 so that when the rear mast 40 is collapsed or retracted downwardly and the carriage 54 is lowered as illustrated in FIG. lathe two rear load lifting forks 70 can be swung manually into inactive positions wherein the straight tines 72 of the respective forks rest horizontally against the upper rear portion of the vehicle chassis structure at opposite sides of the operators seat 20.

When swung manually from the inactive positions illustrated in FIGS. 1 and 2 in solid lines, to active positions illustrated in phantom in FIGS. 1 and 2, the two rear load lifting forks 70 project rearwardly in spaced parallel relation to each other in much the same manner that the forward load lifting forks 36 project forwardly.

The rear cylinders 44, which tip the rear mast 40, and the rear elevating means 48, which raises and lowers the rear load lifter 46 including the rear forks 70 along the mast 40, are controlled as shown by hydraulic controls 74 positioned alongside the operators seat as shown in FIGS. 1 and 2.

The operators seat 20 is swiveled for turning movement between a forward position, illustrated in solid lines in FIG. 2 and a turned or canted position, illustrated in phantom in FIG. 2, which enables the operator to maintain complete control of the vehicle while gaining a clear and unstrainedview to the rear for picking up and depositing a rear load as will appear.

With the rear forks 70 swung downwardly to operating positions illustrated in phantom in FIGS. 1 and 2, the operator lowers the rear lifter 46 includingthe forks 70 to fit under the load to be picked up and maneuvers the vehicleto insert the forks below the load whereupon the rear lifter 46 is raised along the rear mast 40 and the rear mast is tilted inwardly to hold the rear load on the rear forks by'gravity.

With both ends of the vehicle loaded, the center of gravity of the two supported loads is placed generally between the forward and rear support wheels of the vehicle with the consequence that the cumulative vehicle load does not create the unbalanced condition or instability that is so characteristic of conventional fork lift trucks. As a consequence, the load bearing capability of the vehicle 10 is greatly increased and it becomes feasible to move loads over longer distances by use of the vehicle 10. Moreover, the operator need not learn basically new skills as loads are picked up at the rear end of the vehicle and deposited in basically the same manner that loads are picked up and deposited at the front end of the vehicle.

When the distance to be traversedby the loaded vehicle is short, the rear forks 70 can be swung to the outof-the-way stowed positions described. As the vehicle may be used for very short hauls to carry loads at only the front end, a counterweight is supported on the rear of the chassis 12 in the usual'manner, but the mass of the counterweight for a vehicle of a given size may be advantageously minimized by virtue of the balancing effect of the load carried at the rear when longer distances are traversed, in which case vehicle stability is I most important. Power steering is especially advantageous in steering the vehicle when a rear load is carried.

Those skilled in the art will understand and be able to implement the invention without a detailed discussion of particular elements such as the forward elevating mechanism 34 and the rear elevating mechanism 48 which, as such, can be produced with known technology.

The invention is claimed as follows:

1. A balanced fork lift truck comprising a steerable chassis including support wheels therefore, a motor on said chassis connected to propel the latter in forward and reverse directions selectively, a forward tiltable elevator mast supported in a generally upright position on the forward end of said chassis, a forwardly projecting load lifter movably supported on said forward mast to be raised and lowered therealong, first power elevating means connected with said forwardly projecting load lifter to raise and lower the latter along said forward mast, a rear tiltable elevator mast f telescoping construction supported in a generally upright position on the rear end of said chassis and including a movable telescoping section thereof extensible to an upwardly projecting raised position and retractable to a lowered position, a rear load lifter movably supported on said rear mast to be raised and lowered therealong and comprising a carriage guided by said telescoping rear mast section for movement therealong between a raised position and a lowered position, second power elevating means connected to said movable telescoping section of the rear mast and to said carriage to raise and lower both simultaneously and to locate both in lowered stowed positions, said rear load lifter including a pair of L-shaped rear load support forks each having a substantially straight load lifting tine projecting generally at a right angle from adjoining tine support structure of the fork, the ends of said respective forks more remote from said tines thereof being pivotally supported on said carriage to support the forks in downwardly extending load carrying positions with the tines projecting rearwardly; and said L-shaped load support forks being dimensioned to pivot about the pivoted ends thereof upwardly and forwardly, when the carriage is in the lowered stowed position thereof, from the downward load carrying positions of the forks to inactive stowed positions thereof in which the fork tines lie horizontally adjacent the uppermost rear portion of the vehicle chassis. 

1. A balanced fork lift truck comprising a steerable chassis including support wheels therefore, a motor on said chassis connected to propel the latter in forward and reverse directions selectively, a forward tiltable elevator mast supported in a generally upright position on the forward end of said chassis, a forwardly projecting load lifter movably supported on said forward mast to be raised and lowered therealong, first power elevating means connected with said forwardly projecting load lifter to raise and lower the latter along said forward mast, a rear tiltable elevator mast of telescoping construction supported in a generally upright position on the rear end of said chassis and including a movable telescoping section thereof extensible to an upwardly projecting raised position and retractable to a lowered position, a rear load lifter movably supported on said rear mast to be raised and lowered therealong and comprising a carriage guided by said telescoping rear mast section for movement therealong between a raised position and a lowered position, second power elevating means connected to said movable telescoping section of the rear mast and to said carriage to raise and lower both simultaneously and to locate both in lowered stowed positions, said rear load lifter including a pair of Lshaped rear load support forks each having a substantially straight load lifting tine projecting generally at a right angle from adjoining tine support structure of the fork, the ends of said respective forks more remote from said tines thereof being pivotally supported on said carriage to support the forks in downwardly extending load carrying positions with the tines projecting rearwardly; and said L-shaped load support forks being dimensioned to Pivot about the pivoted ends thereof 180* upwardly and forwardly, when the carriage is in the lowered stowed position thereof, from the downward load carrying positions of the forks to inactive stowed positions thereof in which the fork tines lie horizontally adjacent the uppermost rear portion of the vehicle chassis. 